Unraveling the Formation of Core−Shell Structures in Nanoparticles by S-XPS

The combination of the surface sensitivity of X-ray photoelectron spectroscopy (XPS) with the high flux and variable photon energy excitation of Synchrotron radiation (S-XPS) is used to probe the atomic distribution of bimetallic nanoparticles. Based on the energy dependence of the photoemission differential cross section of core level photoelectrons, we propose a methodology to monitor the formation and to evaluate sizes of the core−shell structure. We have successfully applied it to unveil the mechanism involved in the atomic rearrangement of thermally treated Pt0.7Pd0.3 nanoparticles.